This invention relates to novel silyl (meth)acrylate compounds having a bulky substituent group and a method for preparing the same. These novel compounds are useful raw materials for hydrolyzable, self-erodible polymers for use in ship bottom paints.
Ship bottom paints are generally based on hydrolyzable, self-erodible polymers which are usually copolymers of tributyltin methacrylate with methyl methacrylate or the like. These copolymers are hydrolyzed in water to release bis(tributyltin) oxide while the hydrolyzed polymer moiety becomes a water-soluble carboxylic acid and thus dissolved in water so that the coating always presents an active surface. However, the bis(tributyltin) oxide released upon hydrolysis of the copolymers is strongly toxic and imposes concern for water pollution and ecological damages.
There is a need for tin-free polymers. Typical tin-free polymers are disclosed in Japanese Patent No. 3,053,081 and U.S. Pat. No. 4,593,055. Trialkylsilyl (meth)acrylates such as tributylsilyl methacrylate and triisopropylsilyl acrylate are used instead of tributyltin methacrylate and copolymerized with alkyl methacrylates.
However, the trialkylsilyl (meth)acrylates described in these patents fail to give satisfactory results. Even when truisopropylsilyl acrylate which is most bulky and most stable to hydrolysis among them is used, its copolymers still have such a hydrolysis rate that the copolymers are rapidly dissolved away. Thus a demand exists for silyl (meth)acrylate compounds which are more stable to hydrolysis.
An object of the invention is to provide silyl (meth)acrylate compounds which are more stable to hydrolysis and a method for preparing the same.
The inventor has found that a silyl (meth)acrylate compound having attached to a silicon atom one very bulky tertiary hydrocarbon group and two branched hydrocarbon groups each having a hydrocarbon group at xcex1- or xcex2-position or two cyclic hydrocarbon groups is more stable to hydrolysis than the prior art silyl (meth)acrylate compounds.
According to the invention, there is provided a silyl (meth)acrylate compound having a bulky substituent group, represented by the following general formula (1). 
Herein R1 and R2 each are independently a monovalent branched hydrocarbon group having a hydrocarbon group at xcex1- or xcex2-position and having 3 to 10 carbon atoms or a monovalent cyclic hydrocarbon group having 3 to 10 carbon atoms, R3 is a tertiary hydrocarbon group having 4 to 10 carbon atoms, and R4 is hydrogen or methyl.
According to the method of the invention, the silyl (meth)acrylate compound having a bulky substituent group of the formula (1) is prepared by reacting a chlorosilane compound having the following general formula (2):
R1R2R3SiClxe2x80x83xe2x80x83(2)
wherein R1, R2 and R3 are as defined above with acrylic or methacrylic acid in the presence of a basic compound.